Aquastop SHT 216 The Aquastop SHT 216 is a protection system with appliance shutdown. The electronic alarm and switch-off device detects the smallest amounts of liquid and switches off the connected appliance. This activates the appliance's water stop. With acoustic/optical warning. Warning. A solenoid shut-off valve (normally closed) can also be activated via the switchable socket so that the water supply is cut off in the event of water ingress. Your water installation specialist will provide the appropriate shut-off valve.